<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
<style type="text/css">
#canvas{
	background: #000;
}	
</style>				
	</head>
	<body>
<!-- fillStyle	设置或返回用于填充绘画的颜色、渐变或模式
strokeStyle	设置或返回用于笔触的颜色、渐变或模式
shadowColor	设置或返回用于阴影的颜色
shadowBlur	设置或返回用于阴影的模糊级别
shadowOffsetX	设置或返回阴影距形状的水平距离
shadowOffsetY	设置或返回阴影距形状的垂直距离		 -->
	
		<canvas id="canvas" width="" height=""></canvas>
	
	
	<script type="text/javascript">
    var canvas = document.getElementById("canvas");
    var context = canvas.getContext("2d");
    var cx = canvas.width = 400;
    var cy = canvas.height = 400;

    context.beginPath();
    context.arc(100,100,50,0,2*Math.PI,false);
    context.fillStyle = '#fff';
    context.shadowBlur = 20;
    context.shadowColor = '#fff';
    context.fill()
		
	</script>
	</body>
</html>
